Case Study · 2025

Fasting Mastery

Metabolic Health & Mindful Consumption

B2C HealthFlutterBio-Tracking

RoleLead Engineer & Product Architect

StackFlutter · Firebase · RevenueCat

PlatformiOS & Android

CategoryHealth & Wellness

Impact

Results at a Glance

95%

Code Reuse (iOS/Android)

60 FPS

Animation Performance

Local-First

Zero-Latency UX

Overview

Beyond the Stopwatch

Fasting Mastery is a data-driven metabolic health utility. Unlike traditional "stopwatch" fasting apps, it treats human metabolism as a multi-variable equation — allowing users to visualise how caloric intake, macronutrients, and alcohol consumption shift their physiological state in real-time.

The Problem

A Market of Extremes

Missing MiddleHigh-performance users — biohackers and athletes — lacked a tool explaining what was happening internally (autophagy, ketosis) rather than just how long they had fasted.

Alcohol BlindspotMost health apps ignore the physiological delay alcohol causes in metabolic processing, leading to inaccurate fasting data for social users.

UX ProblemExisting apps ranged from overly simplistic "start/stop" timers to aggressive diet-culture tools — neither served the mindful, data-driven user.

User Research

Who We Built For

Bio-OptimizerFocused on longevity and cellular repair. Needs to know exactly when Autophagy peaks to time high-intensity workouts or supplements.

Mindful SocialiteValues health but enjoys social drinking. Needs a non-judgmental view of how a glass of wine affects blood sugar and the fast-to-ketosis timeline.

Key InsightVisualising state ("Cellular Repair Active") is significantly more motivating than displaying elapsed time — this drove the entire product direction.

Core Features

What Makes It Different

Metabolic Phase Engine

Dynamic digestion timers predict physiological phase transitions based on meal composition — not static countdowns.

BAC Tracker

Widmark Formula integration calculates real-time blood alcohol content and visually shows how alcohol delays the fat-burning window.

Local-First Architecture

Instant interactions via SharedPreferences with background Firebase sync — zero latency on the core tracking experience.

Rolling Window Logic

48-hour engine accurately attributes fasting durations across the midnight boundary without manual correction.

Architecture

The Metabolic Phase Engine

A DigestionTimerService calculates transition points across five metabolic states based on intake composition — each macro shifts the window differently.

BMR ProfileMifflin-St Jeor Equation with rigorous floating-point precision across Metric and Imperial conversions

Alcohol ModelWidmark Formula with real-time BAC arc-gauge — clears visually from fasting window as BAC drops

State StoreSharedPreferences for zero-latency local reads; Firestore for cross-device sync and history

Learnings

What We Took Away

Precision Matters

Users sensitive to metabolic data notice even 1% discrepancies — unit-testing floating-point edge cases was non-negotiable.

Visualise State

The custom arc-gauge for BAC proved more effective for behavioural change than tabular data — visualisation beats numbers.

Satiety Correlation

Pro users benefit most from historical analysis showing which meal types led to the longest subsequent fasts without hunger spikes.

Try It

Available Now

Fasting Mastery is live on iOS and Android. Download and start tracking your metabolic phases today.